Portland Shellfish Co. was unable to process shrimp for the bulk of the winter season because of a consent decree reached in January with the FDA over listeria contamination last year.

Owner Jeff Holden says the company spent $500,000 on new equipment, beefed up testing and sanitation, and hired new quality control workers to ensure there’s no future contamination. The processing plants in South Portland and Portland resumed production last week.

Portland Shellfish processes 13 million to 14 million pounds of seafood each year. The FDA says the company ships its products to retailers in Massachusetts, California, Georgia, Illinois, Nevada, Washington, New Jersey and Louisiana.